Plant growth is dictated by both internal and external factors. The internal mechanisms originate in the genetic makeup of the plant and influence the extent and timing of its growth. These internal mechanisms are regulated by signals of various types transmitted within the plant cells, between the cells, or all around the plant itself. The external factors are directly related to the immediate environment surrounding the plant. These external influences affect plant growth and include such factors as light, temperature, water, and nutrients. The external environment can place constraints on the extent to which internal mechanisms can permit the plant to grow and develop, with two of the most important factors being related to the availability of water and nutrient supplies in the soil. Cell expansion is directly related to water supply, and thus any deficit results in a smaller plant. Mineral nutrients are needed for the biochemical processes of the plant. When nutrients are in insufficient supply, growth will be less vigorous, or in extreme cases, it will cease altogether. The nutrients necessary for plant growth include: the primary macronutrients nitrogen (N), phosphorous (P), and potassium (K); the secondary macronutrients calcium (Ca), sulfur (S), and magnesium (Mg); and the micronutrients or trace minerals boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), Molybdenum (Mo), and Selenium (Se). Optimal temperatures are also necessary for plant growth. The required temperature range will depend on the species, but most plants grow slowly at low temperatures, i.e., 0° C. to 10° C., and some tropical plants are damaged or even killed at low, but above-freezing temperatures. Light is also important in the control of plant growth, in that it drives the process of photosynthesis.
Corn steep liquor (CSL) is a liquid by-product of the corn wet-milling process used to obtain corn starch and high fructose corn syrup (HFCS). CSL consists of concentrated corn solubles extracted during a process whereby corn, after having been shelled and air-cleaned, is soaked in water (steeped), and then fractionated into its principal components by a combination of flotation and wet-screening procedures. During steeping, the soluble materials are dissolved, the corn is softened, and its structure weakened and broken, which facilitates the grinding and further separations of its components. The resulting concentrate is crude corn steep liquor, which may be further combined with gluten and fibrous materials to be sold as animal feed, or it can be used for other purposes, with or without further processing. Besides being used as a nutrient for ruminant animals, CSL has also been used in the penicillin industry as a culture medium for penicillin production.
CSL (CAS No. 66071-94-1) is commercially available as approximately 50% water with the rest made up of corn components; water soluble proteins, free amino acids, minerals, vitamins, reducing sugars (e.g., dextrose), and other natural organic acids (e.g., lactic acid). CSL is a viscous slurry with a color ranging from light to dark brown. CSL has a pH of about 4.0 and consists predominantly of naturally occurring nutritive materials such as water soluble proteins, amino acids (e.g., alanine, arginine, aspartic acid, cysteine, glutamic acid, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tyrosine, valine), vitamins (e.g., B-complex), carbohydrates, organic acids (e.g., lactic acid), minerals (e.g., Mg, P, K, Ca, S), enzymes and other nutrients. This CSL is the starting material used in the compositions of the present invention.
Biostimulants are compounds that produce non-nutritional plant growth responses and reduce stress by enhancing stress tolerance. This is in contrast to fertilizers, which produce a nutritional response. Many important benefits of biostimulants are based on their ability to influence hormonal activity. Hormones in plants (phytohormones) are chemical messengers regulating normal plant development as well as responses to the environment. Root and shoot growth, as well as other growth responses are regulated by phytohormones. Compounds in biostimulants can alter the hormonal status of a plant and exert large influences over its growth and health. Sea kelp, humic acids and B Vitamins are common components of biostimulants that are important sources of compounds that influence plant growth and hormonal activity. Antioxidants are another group of plant chemicals that are important in regulating the plants response to environmental and chemical stress (drought, heat, UV light and herbicides). When plants come under stress, “free radicals” or reactive oxygen molecules (e.g., hydrogen peroxide) damage the plants cells. Antioxidants suppress free radical toxicity. Plants with the high levels of antioxidants produce better root and shoot growth, maintain higher leaf-moisture content and lower disease incidence in both normal and stressful environments. Applying a biostimulant enhances antioxidant activity, which increases the plant's defensive system. Vitamin C, Vitamin E, and amino acids such as glycine are antioxidants contained in biostimulants.
The rhizosphere is the region of soil that is immediately adjacent to and affected by plant roots. The rhizosphere is an environment whereby plants, soil, microorganisms, nutrients and water meet and interact. Bacteria present in the rhizosphere feed on shed plant cells as well as proteins and sugars released by plant roots. The interaction between various root microorganisms can play a part in increasing nutrient uptake by plants in nutrient poor environments. Exemplary interactions include symbiotic (e.g., mycorrhizal) and other specific (e.g., nitrogen fixing) associations.
Microbial inoculants are agricultural amendments that use beneficial microbes (e.g., bacteria or fungi) to promote plant health. When added to seeds and soils, microbial inoculants have proven beneficial for use in field crops. Many of the microbes involved form symbiotic relationships with the target crops. While microbial inoculants are applied to improve plant nutrition, they can also be used to promote plant growth by stimulating plant hormone production. Microbial inoculants may also be used to initiate systemic acquired resistance (SAR) of crop species to several common crop diseases. Typical genera of bacterial microorganisms include, for example, Azospirillum, Rhizobium, Bacillus, Pseudomonas, Streptomyces, and Zooglia. Rhizobium is a genus of nitrogen-fixing soil bacteria that form symbiotic associations within nodules on the roots of legumes. This increases nitrogen nutrition and is important to the cultivation of soybeans, chickpeas and many other leguminous crops. For non-leguminous crops, Azospirillum has been demonstrated to be beneficial for nitrogen fixation and plant nutrition. Bacillus, Pseudomonas, and Streptomyces bacteria provide some, if not all, the following benefits: increased plant growth, decomposition of organic matter and pesticide residues, increased nutrient cycling and nitrogen fixation, increased resistance to environmental extremes, increased solubility of minerals for plant uptake, increased production of natural plant growth hormones, improved soil structure, and enhanced seed germination and viability. To improve phosphorous nutrition, the use of phosphate-solubilising bacteria (PSB) such as Agrobacterium radiobacter has also received attention, acting to break down inorganic soil phosphates to simpler forms that enable uptake by plants. Microbial inoculants may also comprise fungi. Several different fungal inoculants have been used to benefit plant health, including the genus Trichoderma and strains such as Arbuscular mycorrhiza and Piriformis indica. Trichoderma provides many of the same benefits to plant health as the aforementioned bacteria, including increasing the plant's resistance to environmental extremes and producing natural plant growth hormones.
Typically, a microbial inoculant contains a “cocktail” of multiple strains of microorganisms, i.e., 40 or more. By inoculating with multiple strains of microorganisms, the underlying problem of not knowing which individual microbe is responsible for the desired plant characteristic or response does not have to be addressed. Presently, microbiologists do not thoroughly understand the individual growth and survival characteristics of each particular beneficial microorganism, including their nutritional and environmental requirements. In addition, there is a general lack of understanding as to the ecological relationships and interactions between the microorganisms themselves. Another prevailing theory is that “singular” (i.e., less than five strains) microbial inoculation is often times not of a sufficient inoculum density to grow, survive and adapt in the soil environment. Therefore, “singular” microbial inoculants are not commonly used in soil or plant amendment products such as biostimulant compositions, plant foods or fertilizers.
Soil bacteria are able to perform a variety of services, including degradation of organic matter, disease suppression, and nutrient transformations inside roots. In general, they are responsible for transforming inorganic constituents from one chemical form to another. The majority of the beneficial soil-dwelling bacteria need oxygen (aerobic), while those that do not require air are referred to as anaerobic. Important soil bacteria include nitrogen-fixing bacteria, nitrifying bacteria, denitrifying bacteria and actinomycetes.
Biostimulants may act to stimulate the growth of microorganisms that are present in soil or other plant growing medium. Prior studies have shown that when biostimulants comprising specific organic seed extracts (e.g., soybean) were used in combination with a microbial inoculant, the biostimulants did not enhance the rhizosphere population of native microbes, but were capable of stimulating growth of microbes included in the microbial inoculant. Thus, it is desirable to obtain a biostimulant, that, when used with a microbial inoculant, is capable of enhancing the population of both native microbes and inoculant microbes.